Final Cut Express - Not asking to auto-conform?

Here's the story -

I make videos for YouTube all the time, I currently film with a Canon Rebel T2i at 1920x1080 at 30fps. When I import my footage, I use MPEG Streamclip to convert it to Apple Intermediate Codec at 100% quality, and "1920x1080 (unscaled)". I never specify a framerate, it usually does it on its own. Whenever I put that footage into Final Cut Express (4.0.1), I drag it into the timeline and it asks me if I want to change the sequence settings to match the settings of that clip, and I always click yes, and it always works fine. However, today I wanted to try out some new settings on my T2i, and the ONLY different thing I did was change from 1920x1080 30fps to 1920x1080 24fps (and also changed some color settings to make it easier to color correct, but that should have no effect). I put the SD card into my computer, as I always do, put the footage into MPEG Streamclip, as I always do, changed the settings to Apple Intermediate Codec, 1920x1080 (unscaled), 100% quality, and no specified framerate, as I always do. The clip imported fine, as it always does. I put it into Final Cut, made a new project, opened the new sequence in the timline, and dragged my clip in. But I got no message asking to change the sequence settings, and the clip was in a square canvas, instead of changing to the normal setting one, which is wide. The quality was also highly reduced. This was abnormal for me, so I tried making a new sequence and importing an old 1920x1080 30fps clip, and sure enough the message popped up asking me to change the sequence settings. It worked fine, but then I tried again in a new sequence to import the NEW clip, and the popup ceased to appear again. I tried restarting my computer, reimporting the clip, checking for Final Cut updates, everything, to no avail. I just can't seem to get the new settings' clip to work.

My question is - why isn't Final Cut working with this clip's minor framerate change, and how do I get it to work again?

Thanks.

P.S. - I've tried looking in the preferences (editing tab) and checking the box to "Always" or "Ask", neither have made anything different.